From Mr Don E. Wayne.

Sir, One of the fallacies governing Christopher Caldwell's attack on the principle that diversity has social value ("Diversity is not black and white", August 11/12) is the notion that diversity is necessarily antithetical to Robert Putnam's concept of "social networks and the associated norms of reciprocity and trustworthiness". This presumes that in an age of globalisation it is still possible to found national identity on a relatively homogenous culture. The US has long experienced the contradiction between a singular ideology of what it is to be an "American" and the lived experience of people in an increasingly heterogeneous society.